Investigating the influence of Taekwondo body protectors size on shock absorption

2020 ◽  
pp. 1-9
Author(s):  
Hee Seong Jeong ◽  
Sae Yong Lee ◽  
Hyung Jun Noh ◽  
David Michael O’Sullivan ◽  
Young Rim Lee
Keyword(s):  
Impact Strength ◽  
Impact Force ◽  
Impact Load ◽  
The Body ◽  
Shock Absorption ◽  
Significance Level ◽  
The Difference ◽  
Maximum Impact Force ◽  
Impact Energies ◽  
The Impact

OBJECTIVE: This study aims to compare and analyze the difference of impact force attenuation according to size and impact location on a Taekwondo body protector. METHODS: Body protectors sized 1 to 5, were impact tested by equipment based on the specifications in the European standard manual (EN 13277-1, 3). The impactor release heights were set to match impact energies of 3 and 15 J. The impactor was made from a 2.5 kg cylindrically cut piece of aluminum. Each body protector was impacted 10 times at the two impact energies and two locations. The differences in performance for each body protector size were compared using a two-way analysis of variance with a significance level of p< 005. The effect sizes were investigated using a partial eta squared value (η2). RESULTS: The significant mean differences between the body protector size and impact area (p< 005) and the average impact time of impact strengths 3 and 15 J were 0.0017 and 0.0012 s, respectively In addition, when an impact strength of 15 J was applied, the maximum resulting impact force exceeded 2000 N for both locations on all sizes. Furthermore, at an impact strength of 3 J size 3 significantly reduced the impact force more than the other sizes; however, size 1 showed the greatest shock absorption at an impact of 15 J. CONCLUSION: The results of this study show that the shock absorption of body protectors does not increase according to size; i.e., a larger body protector does not reduce the impact load more effectively. To improve safety performance, we recommend a maximum impact force of 2000 N or less for all body protectors.

ANALYTICAL SOLUTION OF WEDGE WATER ENTRY BY USING SCHWARTZ–CHRISTOFFEL CONFORMAL MAPPING

2011 ◽  
Vol 02 (03) ◽  
pp. 337-354 ◽  
Author(s):  
PARVIZ GHADIMI ◽  
AMIR SAADATKHAH ◽  
ABBAS DASHTIMANESH
Keyword(s):  
Conformal Mapping ◽  
Impact Force ◽  
Offshore Structures ◽  
Water Entry ◽  
The Body ◽  
Water Impact ◽  
Local Pressure ◽  
Maximum Impact Force ◽  
The Impact ◽  
First Time

Water impact is one of the most critical phenomena from the viewpoint of the structural design of ships and offshore structures. The impact force can impose a large load with high local pressure on the body surface. On the other hand, determination of the maximum impact force during impact and acting point itself is very important in the design of floats. In this paper, the water entry of a two-dimensional wedge section is considered. This study is carried out in the framework of a potential-flow assumption. In particular, water impact on a dropping wedge with a constant velocity is pursued analytically by using the Schwartz–Christoffel conformal mapping. In order to determine a position of the wedge where the instantaneous effective force is largest during the impact, a particular equation is introduced here for the first time. The pressure distribution and maximum impact force are also calculated. The obtained results are compared against other numerical and experimental works and favorable agreement is displayed.

scholarly journals Experimental Study of the Debris Flow Slurry Impact and Distribution

2018 ◽  
Vol 2018 ◽  
pp. 1-15 ◽  
Author(s):  
Haixin Zhao ◽  
Lingkan Yao ◽  
Yong You ◽  
Baoliang Wang ◽  
Cong Zhang
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Impact Force ◽  
Influence Factors ◽  
Flume Experiment ◽  
Middle Point ◽  
Laboratory Flume ◽  
Critical Issues ◽  
Maximum Impact Force ◽  
The Impact

In this study, we present a new method to calculate debris flow slurry impact and its distribution, which are critical issues for designing countermeasures against debris flows. There is no unified formula at present, and we usually design preventive engineering according to the uniform distribution of the maximum impact force. For conducting a laboratory flume experiment, we arrange sensors at different positions on a dam and analyze the differences on debris flow slurry impact against various densities, channel slopes, and dam front angles. Results show that the force of debris flow on the dam distributes unevenly, and that the impact force is large in the middle and decreases gradually to the both sides. We systematically analyze the influence factors for the calculation of the maximum impact force in the middle point and give the quantitative law of decay from the middle to the sides. We propose a method to calculate the distribution of the debris flow impact force on the whole section and provide a case to illustrate this method.

scholarly journals Experimental Study on Axial Impact Mitigating Stick-Slip Vibration with a PDC Bit

2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Yong Wang ◽  
Hongjian Ni ◽  
Yiliu (Paul) Tu ◽  
Ruihe Wang ◽  
Xueying Wang ◽  
...  
Keyword(s):  
Impact Force ◽  
Impact Load ◽  
Similarity Theory ◽  
Impact Frequency ◽  
Stick Slip ◽  
Axial Impact ◽  
Pdc Bit ◽  
Fluctuation Amplitude ◽  
Rotary Speed ◽  
The Impact

Stick-slip vibration reduces the drilling rate of penetration, causes early wear of bits, and threatens the safety of downhole tools. Therefore, it is necessary to study suppression methods of stick-slip vibration to achieve efficient and safe drilling. Field tests show that the use of downhole axial impactors is helpful to mitigate stick-slip vibration and improve rock-breaking efficiency. However, there are many deficiencies in the study of how axial impact load affects stick-slip vibration of a PDC bit. In this paper, based on the two-degrees-of-freedom spring-mass-damper model and similarity theory, a laboratory experiment device for suppressing stick-slip vibration of a PDC bit under axial impact load has been developed, and systematic experimental research has been carried out. The results show that the axial impact force can suppress the stick-slip vibration by reducing the amplitude of weight on bit and torque fluctuations and by increasing the main frequency of torque. The amplitude of impact force affects the choice of the optimal back-rake angle. The impact frequency is negatively correlated with the fluctuation amplitude of the rotary speed. When the impact frequency is greater than 100 Hz, the fluctuation amplitude of the rotary speed will not decrease.

Numerical Analysis on the Response of Deck Plates Laterally Impacted by a Rectangular Indenter

2018 ◽  
Author(s):  
Ling Zhu ◽  
Junying Gao ◽  
Yinggang Li
Keyword(s):  
Permanent Deformation ◽  
Dynamic Loads ◽  
Parametric Studies ◽  
Ice Floes ◽  
Maximum Impact Force ◽  
Impact Energies ◽  
The Impact ◽  
Deformation Modes ◽  
Theoretical Procedure ◽  
Good Agreement

Ship deck plates are often subjected to localized dynamic loads, such as the loads of landing helicopter or impacts of ice floes. In order to investigate the dynamic response of ship plates subjected to such dynamic loads, a series of numerical simulations are performed on ship plates with different thicknesses. Parametric studies are performed on the impact response of plates, including the thickness of the plates, mass and impact velocity of the rectangular indenter. The maximum permanent deflections of the plates are obtained during the simulation. The relation between maximum force and permanent deflection is obtained and the deformation modes are analyzed. A theoretical procedure is developed to predict the deformation of plates with different initial impact energies, and a good agreement between the theoretical and numerical results is obtained. It has also been observed that the thickness of plates has little effect on the dimensionless maximum permanent deformation and dimensionless maximum impact force.

scholarly journals Quality of Life in Patients with Psoriasis Seen in the Department of Dermatology, Antananarivo, Madagascar

2020 ◽  
Vol 2020 ◽  
pp. 1-5
Author(s):  
Fandresena Arilala Sendrasoa ◽  
Naina Harinjara Razanakoto ◽  
Volatantely Ratovonjanahary ◽  
Onivola Raharolahy ◽  
Irina Mamisoa Ranaivo ◽  
...  
Keyword(s):  
Quality Of Life ◽  
Negative Impact ◽  
Young Patients ◽  
The Body ◽  
University Hospital ◽  
Medical Decision ◽  
Cross Sectional ◽  
The Difference ◽  
The Impact

Background. Psoriasis is a chronic, inflammatory, and multifactorial dermatosis that impairs quality of life (QoL). Health-related QoL has become an important element in medical decision-making along with the effectiveness and the harmlessness of the treatments. Objective. To assess the impact of psoriasis in the QoL of patients with psoriasis by using the DLQI scales. Methods. A cross-sectional study from January to June 2018 was conducted in the Department of Dermatology of the University Hospital Joseph Raseta Befelatanana, Antananarivo, Madagascar, including patients more than 18 years old with mild to severe psoriasis. The severity of psoriasis was assessed using the “Psoriasis Area and Severity Index (PASI)”. QoL of patients with psoriasis was evaluated by using the DLQI scales. Results. 80 patients were included, their mean age was 36.5 years, and the male to female was 1.5 : 1. The mean DLQI score was 13.8. Symptoms, feelings, and psychic were the most altered dimensions. QoL was impaired in young patients, single, having medium level education. Even though patients with disease duration more than 5 years had higher DLQI score than other patients, the difference was not statistically significant (p=0.36). Furthermore, the clinical presentation of psoriasis did not influence the patient’s QoL (p=0.73). Patients with nail involvement had QoL impaired but the difference with another localization was not statistically significant (p=0.2). The quality of life was influenced by body area involved. The higher the body surface area involved, the more QoL is impaired (p=0.002). Furthermore, the higher the PASI, the more QoL is altered (p=0.002). Conclusion. Psoriasis has a negative impact in the quality of life in Malagasy patients with psoriasis, especially in younger and single patients. Worse quality of life is correlated to severity of psoriasis.

Finite Element Analysis of a Single-Layer Reticulated Dome under Impact Loading

2010 ◽  
Vol 163-167 ◽  
pp. 327-331 ◽  
Author(s):  
Liang Zheng ◽  
Zhi Hua Chen
Keyword(s):  
Finite Element ◽  
Dynamic Response ◽  
Impact Force ◽  
Impact Load ◽  
Residual Deformation ◽  
Time History ◽  
Single Layer ◽  
Element Analysis ◽  
Deformation Stage ◽  
The Impact

Finite element model of both the single-layer Schwedler reticulated dome with the span of 50m and a Cuboid impactor were developed, incorporating ANSYS/LS-DYNA. PLASTIC_KINEMATIC (MAT_003) material model which takes stain rate into account was used to simulate steel under impact load. The automatic point to surface contact (NODES TO SURFACE) was applied between the dome and impact block. Three stages of time history curve of the impact force on the apex of the single-layer Scheduler reticulated dome including the impact stage, stable stalemate stage, the decaying stage were generalized according to its dynamic response. It must be pointed out that the peak of the impact force of the single-layer reticulated dome increase with the increase of the weight and the velocity of the impact block, but the change of the velocity of the impact block is more sensitive than the change of weight of the impact block for the effect of the peak of the impact force, and a platform value of the impact force of the single-layer reticulated dome change near a certain value, and the duration time of the impact gradually increase. Then four stages of time history curve of the impact displacement were proposed according to the dynamic response of impact on the apex of the single-layer reticulated dome based on numerical analysis. Four stages include in elastic deformation stage, plastic deformation stage, elastic rebound stage, free vibration stage in the position of the residual deformation.

DYNAMIC CHARACTERISTICS MEASUREMENTS OF A FORCE TRANSDUCER AGAINST SMALL AND SHORT-DURATION IMPACT FORCES

2014 ◽  
Vol 21 (1) ◽  
pp. 59-66 ◽  
Author(s):  
Mitra Djamal ◽  
Kazuhide Watanabe ◽  
Kyohei Irisa ◽  
Irfa Aji Prayogi ◽  
Akihiro Takita ◽  
...  
Keyword(s):  
Short Duration ◽  
Dynamic Characteristics ◽  
Impact Force ◽  
Inertial Force ◽  
Small Mass ◽  
Force Transducer ◽  
Force Transducers ◽  
Impact Forces ◽  
Maximum Impact Force ◽  
The Impact

Abstract A method for evaluating the dynamic characteristics of force transducers against small and short-duration impact forces is developed. In this method, a small mass collides with a force transducer and the impact force is measured with high accuracy as the inertial force of the mass. A pneumatic linear bearing is used to achieve linear motion with sufficiently small friction acting on the mass, which is the moving part of the bearing. Small and short-duration impact forces with a maximum impact force of approximately 5 N and minimum half-value width of approximately 1 ms are applied to a force transducer and the impulse responses are evaluated.

Fabrication of Hydraulic Bumper for Anti-Collision in a Vehicle

2015 ◽  
Vol 766-767 ◽  
pp. 499-504 ◽  
Author(s):  
M. Anish ◽  
R. Thamaraikannan ◽  
B. Kanimozhi ◽  
Ham G. Varghese ◽  
Shem G. Varghese
Keyword(s):  
System Design ◽  
Automotive Industry ◽  
Production Cost ◽  
Impact Force ◽  
Impact Load ◽  
Suitable Material ◽  
Fiber Plastic ◽  
The Cost ◽  
The Impact ◽  
Bumper System

Improvement of bumper system is crucial in the automotive industry. The main objectives are to increase the performance of the bumper and also to find a solution to reduce the cost of the bumper thereby facilitating the reduction of production cost. The cost of bumper is high owing to the amount of material used and various processes involved .The new design considers on reducing the amount of material use and adding improved hydraulics instead of normal bumper to give cushioning effect and also assures safety in low speed collision. The new design also improves the ability to absorb more impact load and increase the protection of the front car component. The methodology employed was the study of the front bumper system, design and fabrication. The suitable material that can be used as the bumper in terms of economical but still maintaining the toughness is Plastic-Polycarbonate (Molded) which is not expensive compared to the best material from the analysis of E-Glass Fiber, Plastic-Nylon Type 6/6 and Plastic ABS (Molded). The suitable material to be used for making beam is AISI E52100 Steel. Rearrangement of the mounting positions gives a different effect on the ability to withstand the impact force.

scholarly journals Research on the Method and Model for Calculating Impact Load in the Rockburst Tunnel

Minerals ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 13
Author(s):  
Zhiwei Yan ◽  
Dagang Liu ◽  
Zhilong Wang ◽  
Daming Zhao ◽  
Hongtao Tian
Keyword(s):  
Impact Load ◽  
Design Method ◽  
Pressure Coefficient ◽  
Side Wall ◽  
Calculation Model ◽  
Load Factor ◽  
Circular Tunnel ◽  
Supporting Structure ◽  
The Difference ◽  
The Impact

Among several design methods of tunnel supporting structure, the load-structure method is widely used in different countries, but the determination of load is essential in this design method. The problem of rockburst is becoming more prominent as tunnel engineering enters the deep underground space. However, the research on the impact load on the supporting structure is insufficient in relevant fields. Therefore, from the perspective of energy, this paper deduces the method and model for calculating the impact load of the rockburst tunnel acting on the supporting structure by using the method of structural mechanics first, after the location effect of impact load is determined under different section types and different section sizes. The results indicated that: dynamic load factor K is related to the stiffness EI and supporting size coefficient K0 of the supporting structure, also the difference of impact load in different sections is proved. Tunnel rockburst-prone location is related to lateral pressure coefficient, thus when λ = 1, the probability of rockburst in the whole circular tunnel is the same, while side wall and vault are prone to rockburst in single-track horseshoe tunnel, and the side wall is prone to rockburst in double-track horseshoe tunnel; furthermore when λ > 1, the vault and the inverted arch are prone to rockburst; additionally, when λ < 1, the rockburst is most likely to occur in the arch waist of the circular tunnel and the side walls and the arch waist of the horseshoe tunnel. Finally, the rockburst tunnel’s local load-structure calculation model and the calculation process based on the model are provided.

scholarly journals Dropped Object Impact Analysis Considering Frequency and Consequence for LNG-FPSO Topside Module

2021 ◽  
Vol 11 (16) ◽  
pp. 7753
Author(s):  
Kwangkook Lee ◽  
Hyunsu Ryu
Keyword(s):  
Impact Energy ◽  
Impact Analysis ◽  
Quantitative Risk Assessment ◽  
Production Area ◽  
The Difference ◽  
Offshore Industry ◽  
Impact Energies ◽  
The Impact ◽  
External Loads ◽  
Specific Orientation

Recently, quantitative risk assessment (QRA) has been widely used as a decision-making tool in the offshore industry. This study focused on analyzing dropped objects in the design of a modern offshore platform. A modified QRA procedure was developed for assessing production module protection against accidental external loads. Frequency and consequence analyses were performed using the developed QRA procedure. An exceedance curve was plotted, and a high-risk management item was derived through this process. In particular, simulations and experiments were used to verify the difference between the potential and impact energies according to drop orientation. When the object dropped in a specific orientation, the impact energy was confirmed to be up to 4.7 times greater than the potential energy. To reflect the QRA results in structural design, the proposed procedure should be used to calculate the maximum impact energy. The proposed procedure provides a step-by-step guide to assess the damage capacity of a production area as well as the damage frequency and consequences.

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