cantilever length
Recently Published Documents


TOTAL DOCUMENTS

65
(FIVE YEARS 26)

H-INDEX

7
(FIVE YEARS 1)

Author(s):  
Sergij Yurijovich Pogorilov ◽  
Valerij Lvovich Khavin ◽  
Inna Petrovna Khavina

One of the main structural elements of metalworking machines is the spindle assembly (spindle), which is used to hold cutting tools or workpieces. The rigidity of the spindle assembly plays a decisive role in ensuring the accuracy and efficiency of the machine as a whole. The assessment of the spindle shaft stiffness is carried out on the basis of the analysis of the static bending of the spindle shaft, which made it possible to formulate and solve the problems of optimizing the spindle shaft according to the stiffness characteristics for two supporting structures on nonlinear elastic supports. To determine the stiffness of roller bearings, the work uses the dependence obtained on the basis of solving the problem of contact interaction of an elastic steel cylinder with curvilinear elastic steel half-spaces. For the considered design scheme, the optimization goals were chosen for the conditions of the smallest displacement of the end section of the spindle shaft console, the achievement of the minimum angle of rotation in this section or the minimum of their normalized superposition, which ensures maximum rigidity in the processing zone. Consideration has also been given to minimizing the swing angle at the front support to maximize bearing life. Mathematically, the problem is presented in the form of minimizing one of the 4 proposed objective functions by changing the variable parameters - the length of the cantilever and the value of the inter-support distance, represented as dimensionless quantities - the cantilever coefficient and the inter-support distance coefficient. Minimum and maximum values ​​of the cantilever length and shaft span were considered as constraints on the variable parameters. Varying the console coefficients and the inter-support distance was carried out by the method of sequential enumeration within the specified constraints, the solution of optimization problems is presented in a graphical form. The solution to the problem of shaft bending was carried out on the basis of the equation of the bent axis of the beam in the framework of the Euler - Bernoulli hypotheses and presented in an analytical form together with analytical dependencies for calculating the radial stiffness of a roller bearing as a function of the supporting force acting on it. The algorithm for solving optimization problems is implemented in the MatLAB package. Optimal solutions have shown that the minimum of the combined functions, consisting of the sum of the relative deflection values ​​at the end of the console and the angles of rotation at the end of the console and on the front support, is achieved at the same variable parameters as the minima of the angles of rotation at the end of the console and on the front support. The proposed approach to the design of the shafts of spindle units of metal-cutting machines, which are optimal in terms of rigidity characteristics, forms a tool for a reasonable choice of bearings and design parameters of spindle shafts.


2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Jiaxin Dang ◽  
Min Tu ◽  
Xiangyang Zhang ◽  
Qingwei Bu

The conditions of the hard roof in my country vary greatly, ranging from a few meters to tens of meters or even hundreds of meters in thickness. The coal reserves under the hard roof account for about one-third of the total reserves. At present, nearly 40% of fully mechanized mining faces that belong to the hard roof working face has the problem of mining in the hard roof working face. This has a serious impact on the load-bearing stability of the fully mechanized support, and it is urgent to solve the problem of strong underground pressure dynamic disaster under the condition of the hard roof. Based on the research background of 11129 working face in Zhangji Coal Mine in Huainan, this paper constructs a mechanical model of the interaction between the cantilever beam of the hard roof of the stope and the support and then the force distribution equation of the bearing capacity of the supports at different positions of the roof during the periodical rotation of the working face is obtained, which is combined with numerical simulation and engineering site to verify. The research results show that the bearing stability of the support is significantly affected by factors such as the buried depth H, the roof elastic modulus E, the roof thickness h, and the roof cantilever length l0, but most of the influencing factors belong to the geological occurrence conditions of the coal seam itself. Presplit blasting of the roof in advance can effectively destroy the integrity of the roof itself and reduce the periodic breaking distance, thereby improving the apparent environment of roof rock pressure and reducing the force on the working face support. According to the specific geological environment of the 11129 working face, the cutting plan of the cut hole is given out, along the groove 0∼200 and 200∼700 m of the concrete presplitting blasting. The stent force of the top-cutting section fluctuates in the range of 3360.8–4347.9 kN in the range of control top distance (5275∼6175 mm). The load-bearing pressure of the stent before top-cutting is about 1.8 times of that after top-cutting. The pressure distribution of the hydraulic support in the numerical simulation stope is approximately “Λ” in the middle and the low on the two sides. The simulated value is slightly smaller than the theoretical calculation value. The reason is that the goaf is backfilled during the simulation process, and the roof has a certain ability to bear the load. Real-time understanding of the “roof-support” mechanical relationship can effectively ensure the safe and efficient mining of the 11129 working face and also provide experience for the subsequent mining of group B coal in the later period.


2021 ◽  
pp. 1-26
Author(s):  
Hanbin Yin ◽  
Yin Yao ◽  
Yazheng Yang ◽  
Zhilong Peng ◽  
Shaohua Chen

Abstract Different from the system of a single-layer elastic film on a rigid substrate, it is difficult to determine which interface will debond in a bilayer or multilayer film-substrate system. A peeling model of a bilayer elastic film on a rigid substrate is established in the present paper, in order to predict which interface debonding occurs first. The interfacial competitive debonding mechanism is theoretically analyzed with the help of the beam bending theory. A criterion of which interface debonding occurs first is proposed. It is found that the interfacial debonding path is mainly controlled by five dimensionless parameters, i.e., the strength ratio and the critical separation distance ratio of the upper and lower interfaces, the Young's modulus ratio and the thickness ratio of the upper and lower films, and the possible initial cantilever length for ease of loading. The corresponding competitive debonding map is well obtained. From the map, which interface debonds first can be easily predicted. It is interesting to find that the interfacial debonding path can be well tuned by any one of the five parameters. The results of the finite element calculation further confirm the theoretical predictions. The present work can not only provide a theoretical method to determine the interfacial debonding path but also be helpful for the optimal design of multilayer film-substrate systems in practical applications.


Author(s):  
Song Li ◽  
Xinle Yang ◽  
Weikang Li ◽  
Meiling Tang

Studies show that operating stress and natural frequency of the turbocharger impeller are two key parameters that affect the service life of the turbocharger. In this regard, NREC and ANSYS software are utilized in the present study to design impellers and calculate the impeller stress, natural frequency, and the inertia moment of the impeller for each baseline impeller and their modifications. Furthermore, modal tests are carried out to verify the simulation results. Finally, the compressor characteristic maps before and after the blade gradient angle optimization are compared. Obtained results show that compared with the cantilever length, the blade thickness has a remarkable influence on the blade gradient angle. Moreover, it is found that the correlation between the blade gradient angle and the first-order frequency multiplication ratio is linear. As the blade gradient angle increases, the maximum stress at the blade root of the compressor initially decreases and then increases. The value of the blade gradient angle varies within the range of 2.288°–3.955°. Moreover, the closer the gradient angle to 3.26°, the smaller the maximum equivalent stress of the impeller, and the higher the impeller strength. The greater the thickness of the blade, the longer the cantilever length of the impeller, and the greater the inertia moment. Optimizing the blade gradient angle can improve the efficiency of the compressor without changing the pressure ratio and flow rate. It should be indicated that error between the results from the simulation and the experiment is within the range 1.736%–1.254%. Therefore, the calculation results are reliable. It is concluded that the regular pattern of the blade gradient angle affects the compressor impeller stress and its natural frequency. The present article is expected to provide a helpful theoretical basis for designing an optimized compressor impeller.


2021 ◽  
Author(s):  
Hanieh Pourmand

Clause 5.7.1.3 of the Canadian Highway Bridge Design Code (CHBDC) specifies an equation for the calculation of transverse moment intensity (My) in the deck slab cantilever due to truck loading in a slab-on-girder bridge system. Also, it states that the transverse moment intensity shall be assumed 2My for the locations within a distance equal to cantilever length of the transverse free end of the deck slab cantilever. However, CHBDC design values do not consider the effects of barrier length, variable thickness of the barrier wall and shape of the cantilever’s edge stiffening on the response. In addition, the longitudinal moment on the deck slab cantilever due to truck loading is as yet unavailable. Thus, a parametric study was conducted, using the finite element modelling, to investigate the effect of these key parameters in the transverse and longitudinal moments at the region of the transverse free edge of deck slab cantilever. Based on the data generated from this parametric study, imperial equations for the transverse and longitudinal moments at the transverse end of the deck slab cantilever were deduced.


2021 ◽  
Author(s):  
Hanieh Pourmand

Clause 5.7.1.3 of the Canadian Highway Bridge Design Code (CHBDC) specifies an equation for the calculation of transverse moment intensity (My) in the deck slab cantilever due to truck loading in a slab-on-girder bridge system. Also, it states that the transverse moment intensity shall be assumed 2My for the locations within a distance equal to cantilever length of the transverse free end of the deck slab cantilever. However, CHBDC design values do not consider the effects of barrier length, variable thickness of the barrier wall and shape of the cantilever’s edge stiffening on the response. In addition, the longitudinal moment on the deck slab cantilever due to truck loading is as yet unavailable. Thus, a parametric study was conducted, using the finite element modelling, to investigate the effect of these key parameters in the transverse and longitudinal moments at the region of the transverse free edge of deck slab cantilever. Based on the data generated from this parametric study, imperial equations for the transverse and longitudinal moments at the transverse end of the deck slab cantilever were deduced.


2021 ◽  
Author(s):  
Ivan Micovic

This study recommends new simplified equations for the transverse moment and shear force at the base of the cantilever overhang due to applied vertical truck loading. This was made possible through a parametric study that utilized finite-element modelling on bridge deck cantilevers with variable lengths and slab thicknesses. Different end stiffening arrangements were considered that are encountered in practice, and included but were not limited to the PL-1, PL-2 and PL-3 New Jersey-type barriers walls, a PL-2 parapet, and a curb supporting intermittent steel posts carrying a guardrail. The barrier length changed from 3 to 12 m and the cantilever length ranged from 1.0 to 3.75 m. Further to the empirical expressions that had been developed, the study is supported by tables that were developed to readily design the cantilever slab, based on vertical loads due to vertical truck loading, as well as horizontal railing loads against the barrier wall.


2021 ◽  
Author(s):  
Ivan Micovic

This study recommends new simplified equations for the transverse moment and shear force at the base of the cantilever overhang due to applied vertical truck loading. This was made possible through a parametric study that utilized finite-element modelling on bridge deck cantilevers with variable lengths and slab thicknesses. Different end stiffening arrangements were considered that are encountered in practice, and included but were not limited to the PL-1, PL-2 and PL-3 New Jersey-type barriers walls, a PL-2 parapet, and a curb supporting intermittent steel posts carrying a guardrail. The barrier length changed from 3 to 12 m and the cantilever length ranged from 1.0 to 3.75 m. Further to the empirical expressions that had been developed, the study is supported by tables that were developed to readily design the cantilever slab, based on vertical loads due to vertical truck loading, as well as horizontal railing loads against the barrier wall.


Molecules ◽  
2021 ◽  
Vol 26 (8) ◽  
pp. 2259
Author(s):  
Ibraheem F. Alshiddi ◽  
Syed Rashid Habib ◽  
Muhammad Sohail Zafar ◽  
Salwa Bajunaid ◽  
Nawaf Labban ◽  
...  

The fracture resistance of computer-aided designing and computer-aided manufacturing CAD/CAM fabricated implant-supported cantilever zirconia frameworks (ISCZFs) is affected by the size/dimension and the micro cracks produced from diamond burs during the milling process. The present in vitro study investigated the fracture load for different cross-sectional dimensions of connector sites of implant-supported cantilever zirconia frameworks (ISCZFs) with different cantilever lengths (load point). A total of 48 ISCZFs (Cercon, Degudent; Dentsply, Deutschland, Germany) were fabricated by CAD/CAM and divided into four groups based on cantilever length and reinforcement of distal-abutment: Group A: 9 mm cantilever; Group B: 9 mm cantilever with reinforced distal-abutment; Group C: 12 mm cantilever; Group D: 12 mm cantilever with reinforced distal-abutment (n = 12). The ISCZFs were loaded using a universal testing machine for recording the fracture load. Descriptive statistics, ANOVA, and Tukey’s test were used for the statistical analysis (p < 0.05). Significant variations were found between the fracture loads of the four ISCZFs (p = 0.000); Group-C and B were found with the weakest and the strongest distal cantilever frameworks with fracture load of 670.39 ± 130.96 N and 1137.86 ± 127.85 N, respectively. The mean difference of the fracture load between groups A (810.49 + 137.579 N) and B (1137.86 ± 127.85 N) and between C (670.39 ± 130.96 N) and D (914.58 + 149.635 N) was statistically significant (p = 0.000). Significant variations in the fracture load between the ISCZFs with different cantilever lengths and thicknesses of the distal abutments were found. Increasing the thickness of the distal abutment only by 0.5 mm reinforces the distal abutments by significantly increasing the fracture load of the ISCZFs. Therefore, an increase in the thickness of the distal abutments is recommended in patients seeking implant-supported distal cantilever fixed prostheses.


Sign in / Sign up

Export Citation Format

Share Document