Numerical simulation of crashworthiness parameters for design optimization of an automotive crash-box

Automotive manufacturers rely on rigorous testing and simulations to construct their vehicles durable and safe in all aspects. One such vital factor is crash safety, otherwise known as crashworthiness. Crash tests are conventional forms of non-destructive methods to validate the vehicle for its crashworthiness and compatibility based on different operating conditions. The frontal impact test is the most primary form of crash test, which focuses on improving passenger's safety and comfort. According to NHTSA, a vehicle is rated based on these safety criteria, for which automobile manufacturers conduct a plethora of crash-related studies. Numerical simulation aids them in cutting down testing time and overall cost endured by providing a reliable amount of insights into the process. The current study is aimed at improving the crashworthiness of a crash box in a lightweight passenger car, such that it becomes more energy absorbent in terms of frontal impacts. All necessary parameters such as energy absorption, mean crush force, specific energy absorption, crush force efficiencies are evaluated based on analytical and finite element methods. There was a decent agreement between the analytical and simulation results, with an accuracy of 97%. The crashworthiness of the crash box was improved with the help of DOE-based response surface methodology (RSM). The RSM approach helped in improving the design of the crash box with enhanced EA & CFE by 30% and 8.8% respectively. The investigation of design variables on the energy absorption capacity of the thin-walled structure was also done. For the axial impact simulations, finite element solver Virtual Performance Solution − Pam Crash from the ESI group is used.

The Effects of Cannabis Use Frequency and Episodic Specificity Training on the Recall of Specific and Rewarding Events

Background: Growing evidence implicates subjective episodic memory, the retrieval of detailed, integrated, and personally relevant past events, as a marker of cognitive vulnerability in mental disorders. Frequent and problematic cannabis use is associated with deficits in objective episodic memory (verbal memory), but the relationship between subjective episodic memory deficits and frequency of cannabis use is unknown. Further, whether a brief intervention designed to enhance the specificity of event retrieval, such as the Episodic Specificity Induction (ESI), might effectively target such deficits among regular cannabis users is unexamined. This study was designed to examine subjective episodic memory as a potential marker of cognitive vulnerability among frequent cannabis users.Methods: Active cannabis users (n = 133) recruited from Amazon Mechanical Turk or Qualtrics Panels were randomized to receive an ESI-control or ESI session and were separated into those who used cannabis 1–25 days in the past month (low to moderate frequency group) and those who used 26–30 days (high frequency group), which facilitated a low to moderate use/ESI-control group (n = 78), low to moderate use/ESI group (n =15), high-use/ESI-control group (n = 20), and high-use/ESI group (n = 20). Following the ESI or ESI-control intervention, participants selected four, positive events from the prior day, described the who, what, and where of the events, and rated how specific (vividness) and rewarding (enjoyable, importance, and exciting) each event was on a 0–100 scale. Four two-way ANCOVAs (demographics and problematic cannabis use covariates) were performed to examine the effects of frequency of cannabis use group and ESI group on the specificity and reward ratings.Results: Lower vividness and excitement ratings were reported for those with high relative to low to moderate cannabis use frequency patterns (p < 0.05). Those who received ESI reported greater vividness, excitement, and importance ratings than the ESI-control group (p < 0.01). No significant interactions between frequency and ESI were found.Conclusion: Findings from the current exploratory study provide initial evidence suggesting that more frequent cannabis use may be associated with the retrieval of less specific and rewarding events relative to less frequent users. Further, ESI may improve such deficits. Future studies that recruit larger and more clinically serious samples of cannabis users appear warranted.

Effectiveness of epidural steroid injection in patients with lumbar herniated intervertebral disc under a “wait-and-see” policy

Background There are no consensus and guidelines on the optimal interval of repeat epidural steroid injections (ESI) for patients with lumbar herniated intervertebral disc (HIVD) who respond to initial ESI. Purpose To evaluate the effectiveness of ESI in patients with HIVD under a “wait-and-see” policy, i.e. as-needed injections not on a predetermined schedule. Material and Methods A total of 592 patients with lumbar HIVD received spine injections between January and December 2017. After excluding patients with excellent (no pain) or poor (>70% residual symptoms) response in the two- or three-week pain assessment, the data of 141 responders were analyzed (60 men, 73 women; age = 50.55±17.25 years). We divided patients into wait-and-see (n=124) and early repeat-ESI (n=17) groups, who received repeat ESIs within three weeks. Evaluations of characteristics and outcomes were performed with the chi-square test or independent Student’s t-test. Results Six patients (4.8%) in the wait-and-see group and 1 (5.9%) in the early repeat-ESI group underwent operation within one year ( P=0.85). A mean of 1.52±0.82 ESIs was performed in the wait-and-see and a mean of 2.29±0.47 ESIs in the early repeat-ESI group over one year ( P<0.001). The time interval between the first and second ESIs was longer in the wait-and-see group than in the early repeat-ESI group (97.15 vs. 15.47 days, P<0.001). Seventy-eight patients (62.9%) in the wait-and-see group could control their pain with a single ESI. Conclusion A “wait-and-see” policy could be an effective pain management option for patients with lumbar HIVD who respond to initial ESI.

Experimental and simulation study of phase transformation in thermite welded railway steel heat-affected zone regions

Rail transportation has been an emerging and promising transportation method for economic development in Thailand and several countries. Thermite welding is one of the major welding and joining processes used to weld rail steel both during construction and maintenance. Unlike most welding processes in which heat is generated by electrical energy, thermite welding use heat generated during the chemical reactions between iron oxide and aluminum or other metallic compounds to create the weld. The amount of heat generated is thus depended on the composition and ratios of iron oxide, aluminum, as well as other metallic compounds mixed in the thermite powder. In addition, the size, shape, and material used for thermite mold could also play an important role in the heat transfer process during thermite welding of rail steel. In this research, SYSWELD software developed by ESI Group is used to perform thermal-mechanical-metallurgical welding simulation during thermite welding of rail steel. The current article presents that research methodology used to formulate the prediction of microstructure developed in the heat-affected zone regions of thermite welding of railway steel. It is noted that this work attempts to evaluate how preheat, heat generation during chemical reaction, and possible post-weld heat treatment could be performed to controlled the microstructure of pearlitic rail steel using SYSWELD software. The results of this on-going research will be used as the baseline for future development of structural integrity program for improving joining of rail steel such as the design and selection of welding processes and materials involved for rail construction, especially when appropriate grades and welding procedures of rail steels must be chosen and developed to withstand the actual loading conditions.

Numerical Verification of Tests on the Influence of the Imposed Thermal Cycles on the Structure and Properties of the S700MC Heat-Affected Zone

The article presents the results of studies on the influence of simulated thermal cycles parameters on the structure and properties of the heat-affected zone (HAZ) of thermo-mechanically rolled S700MC steel. For this purpose, resistance heating tests of the tested samples were carried out to determine the effect of maximum temperatures of the imposed thermal cycles with different maximum temperatures at a constant cooling time in the temperature range between 800 and 500 °C (t8/5) and to study the influence of changes of this time on the structure and hardness as well as the tensile strength, elongation and toughness of the simulated HAZ in S700MC steel. The results of the tests, were supported by the results of finite element method (FEM) analyses in the VisualWeld (SYSWELD Code) software of the ESI Group. Selected heat distributions during heating, distributions of individual metallurgical phases and hardness were compared with results from real tests. On the basis of the results presented, an attempt was made to explain the decrease in mechanical and plastic properties in the HAZ area caused by the influence of the welding heat cycle.

Evaluating the Accuracy of RANS Wind Flow Modeling Over Forested Terrain—Part 1: Canopy Model Validation

This study uses the Reynolds-averaged Navier–Stokes (RANS) equations to validate a canopy model by computing a fully developed wind flow within and above a horizontally homogeneous dense forest as in the work of Dalpé and Masson. The model is paired with a modified k–ε turbulence closure. A set of boundary conditions (BCs) that rely on the law of the wall for a sustainable atmospheric boundary layer (ABL) is used. All simulations are conducted in the open source software OpenFOAM v.2.4.0 (OpenCFD Ltd (ESI Group)). Two practical aspects are considered in the validation process. First, an accurate leaf area index (LAI) integration to exactly fit the wind shear is evaluated. Since the physical foliage parameters may not be accessible for all type of forests, a generic leaf area density α distribution is tested. The results of this test show that a generic distribution is sufficient for preliminary analyses to improve accuracy of wind flow predictions over forested terrain. Second, the approach of Dalpé and Masson is limited to cyclic BCs which are not practical for real sites. For cases without cyclic BCs, imposing a proper slope on the inlet velocity profile is of high importance. This condition can be achieved through adjustment of the roughness length at the inlet.

The Numerical Simulation of the Deep Drawing Process and its Verification by the Adaptation of the Laminated Tooling Concept

The paper deals with numerical simulation and its verification when designing production the gutter corner for the rainwater systems. The deep drawing process has been simulated in Pam Stamp 2G software by ESI Group and the part and blank geometry, friction and process parameters have been optimized. Then, those parameters and the die geometry were verified by experiment when lamination tooling concept has been adapted. The metal laminated tooling technology was used for production of the punch by applying the laser cutting, assembling and joining. The experiments were done using hot deep galvanized steel sheet DX54D+Z with thickness 0.6 mm.

Randomized Controlled Study of Percutaneous Epidural Neuroplasty Using Racz Catheter and Epidural Steroid Injection in Cervical Disc Disease

Background: The efficacy of lumbar percutaneous epidural neuroplasty (PEN) as a minimally invasive technique has been relatively well investigated, but the clinical effectiveness of cervical PEN (C-PEN) has yet to be established. Objective: The purpose of this study was to compare clinical outcomes between C-PEN and cervical epidural steroid injection (C-ESI). Study Design: Randomized control study. Setting: University hospital center. Methods: Eighty patients with neck pain from single level cervical disease with and without radiculopathy were included in this study. Patients were randomly assigned into 2 groups: C-PEN or C-ESI. Clinical outcomes were assessed according to Neck Disability Index (NDI) score and Visual Analog Scale (VAS) score for arm pain until 12 months after treatment. Results: All C-PEN and C-ESI groups showed better NDI recovery and greater reduction in VAS score at postoperative 6 months (P < 0.001). The C-PEN group demonstrated better NDI score at postoperative 6 months than the C-ESI group (P = 0.014), while there were no differences at 2, 4, and 12 months. Additionally, the C-PEN group showed lower VAS scores at all follow-up intervals compared to the C-ESI group (P < 0.050). Symptom relief was sustained for a significantly longer duration in the C-PEN group than in the C-ESI group (23.4 vs. 20.5 weeks, P < 0.001). Limitations: The follow-up period was relatively short with a small sample size, and the grade of cervical disc disease, root compression, and disc degeneration grade were could not considered in this study. Conclusions: C-PEN was superior to C-ESI in terms of better NDI recovery (at 6 months) and greater reduction in VAS score (until 12 months) in treating single level cervical disc herniation. Better outcomes with C-PEN may have been achieved via a more localized selective block in the epidural space closer to the dorsal root ganglion and ventral aspect of the nerve root. Key words: Cervical, cervical disc disease, pain management, percutaneous epidural neuroplasty, percutaneous adhesiolysis, epidural steroid injection

Investigation on Weld Induced Distortion of Butt and T-Joints Using Thermo-Elastic-FEM and Experimental Study

In this paper, the capability of linear thermo-elastic numerical analysis method to estimate the welding deformations was investigated. The weld induced deformation is considered as the major stumbling block that can affect the dimensional accuracy. Based on this fact, welding distortion is necessarily to be predicted, if experimental investigation becomes expensive, to minimize the negative effects, improve the quality of welded parts and finally to reduce production cost. In this study, the welding distortions on butt and T-joints with thicknesses of 4 mm and 6 mm were simulated using relatively new FEM software WELD PLANNER developed by ESI Group. The material used for the simulation was low Carbon steel. By comparing the results between simulation and experiment, it was found out that this software provided immediate solution for computational analysis time and was capable to predict the distortion within acceptable accuracy.