Fatigue design for plug/ring type gas welded joints of sts301l including welding residual stresses

This paper presents a fatigue design method for plug and ring type gas welded joints, which incorporates welding residual stress effects. A non-linear finite element analysis (FEA) was first performed to simulate the gas welding process. The numerically predicted residual stresses of the gas welds were then compared to experimental results measured using a hole drilling method. In order to evaluate the fatigue strength of the plug and ring type gas welded joints, a stress amplitude (σ _a ) _R taling the welding residual stress of the gas weld into account was introduced and is based on a modified Goodman equation incorporating the effect of the residual stress. Using the stress amplitude (σ _a ) _R , the ΔP-N _f relations obtained from fatigue tests for plug and ring type gas welded joints having various dimensions and shapes were systematically rearranged into (σ _a ) _R -N _f relations. It was found that the proposed stress amplitude (σ _a ) _R could provide a systematic and reasonable fatigue design criterion for the plug and ring type gas welded joints.     

Fatigue strength assessment including welding residual stress of spot welded joints subjected to cross-tension loads

This paper presents a method to assess of fatigue strength for resistance spot welded joints, which incorporates welding residual stress effects. To achieve this, first, a non-linear finite element analysis (FEA) was performed to simulate the spot-welding process. To validate the FEA results, the numerically calculated welding residual stresses of spot welds were then compared with experimental results measured by X-ray diffraction method. The residual stress distributions showed good agreement between calculations and experiments. To evaluate the effects of welding residual stress on the fatigue design criterion of resistance spot welded joints subjected to cross-tension load, the stress amplitude (σ_a-res) taking into account welding residual stress at a spot weld was proposed based on a modified Goodman equation incorporating the residual stress effect. Using the stress amplitude σ_a-res at the nugget edge of a spot weld, the ΔP ? N_f relations obtained as the fatigue test results for spot welded joints were systematically rearranged to the σ_a-res ? N_f relation. It was found that the proposed stress amplitude (σ_a-res) provides more reasonable and accurate fatigue design criterion of spot welded joints subjected to cross-tension load.     

汽车结构中焊缝疲劳寿命预估

介绍了焊缝疲劳寿命估算的有效方法——VOLVO方法的步骤及原理。采用该方法可计算出真实运行工况下结构焊缝的疲劳损伤和寿命情况。针对某商用车后桥壳上的焊缝连接,利用VOLVO方法进行了焊缝寿命预估,得到了整个焊缝的损伤和寿命分布,通过与台架试验中桥壳失效部位的对比表明,预估结果与试验结果一致。     

Fatigue life prediction based on the rainflow cycle counting method for the end beam of a freight car bogie

This paper presents a system for treating of the actual measured data for load histories. The approach consists of two steps: stress analysis and fatigue damage prediction. Finite element analysis is conducted for the component in question to obtain detailed stress-strain responses. A significant number of failures occurred in a brake end beam which led to economic losses and disruption of service. The cracks appeared to be fatigue cracks caused by the dynamic load produced in the loaded bogie frame. Strain gauge data were analyzed, and fatigue cycles were calculated from this data. Rainflow cycle counting was used to estimate cumulative damage of the end beam under in-service loading conditions. The fatigue life calculated with the rainflow cycle counting method, the P-S-N curve, and the modified Miner’s rule agreed well with actual fatigue life within an error range of 2.7%~31%.     

基于道路载荷谱的车身疲劳寿命改进研究

叙述了基于实测道路载荷谱将CAE疲劳寿命预测技术与整车道路模拟试验相结合的方法对某车型车身进行疲劳失效再现和改进设计的过程,改进后的车身分别通过了整车台架试验和试车场道路耐久试验,解决了开发过程中的实际问题。虚拟分析识别出的失效位置与物理试验失效结果一致,可以利用其部分替代物理试验来进行车身的改进设计。实践证明CAE疲劳寿命预测技术与整车道路模拟试验相结合的方法能够有效减少车身开发中的试验数量、缩短开发周期。     

Impact behavior modeling of motorcycle front wheel-tire assembly

Experiments were conducted to investigate the influence of certain parameters that affect the impact response of the motorcycle front wheel-tire assembly under various impact conditions. Impact tests were conducted according to 2 _ν ^{5 − 1} fractional factorial design using a pendulum impact test apparatus with impact speed, impact mass, tire inflation pressure level, striker geometry, and impact location as design factors. Significant factors influencing the response of the wheel-tire assembly were identified. Coefficients for each factor were also determined, and empirical models were then developed for each response. An analysis indicates that the developed models fit well within the experimental ranges of the respective factors. However, for several interaction effects, the models become unrealistic, whereby they give certain deformation values when approaching zero impact mass and/or zero impact velocity. This is not consistent with the mechanics of the physical world, as there should not be any significant deformation when delivered impact energy is small enough. Efforts have been made in developing better models to resolve the inconsistency and to include a wider range, especially considering the case of the lower limit of experimental factors, which are an impact mass of 51.18 kg and/or an impact velocity of 3 m s⁻¹ (10.8 km/h) down to zero. The minimum amount of impact energy required to produce the onset of observable deformation on the wheel was incorporated in the development of new models. Finally, the present models have been developed not only to cover the lower regions but also to range up to the upper limits of the factors, which are an impact mass of 101.33 kg and an impact velocity of 6 m s⁻¹ (21.6 km/h).     

基于名义应力法的疲劳卡片构建方法研究

基于有限元的疲劳寿命预测可应用于各行业,疲劳寿命预测精度的提高,离不开有效的材料疲劳卡片,疲劳卡片反映了载荷水平与疲劳寿命的关系。通过设计合理的材料试样的疲劳试验,结合试验与有限元计算,计算不同损伤参量创建应用于疲劳寿命分析的材料疲劳卡片,同时对疲劳卡片的仿真精度进行了验证。结果表明,基于名义应力法构建的疲劳卡片具备较高的预测精度,结合材料试验数据与仿真结果构建的多应力比S-N疲劳卡片,可用于其他适用于应力疲劳分析的零部件疲劳寿命分析,为提高零部件疲劳寿命预测精度提供新的技术途径,为零件的前期结构设计提供参考,可在不同领域进行推广并开展进一步分析研究。     

钢筋混凝土桥面板疲劳数值分析方法

为了模拟车辆荷载作用下桥面板的疲劳损伤退化过程,提出了针对公路钢筋混凝土桥面板疲劳失效过程的数值分析方法。首先在各国相关试验与研究的基础上,通过编制合理的荷载谱,将复杂的车辆荷载进行简化等效;然后提出了高周循环荷载下受弯构件中钢筋与混凝土材料的疲劳本构关系,基于ABAQUS软件对一试验板建模分析,验证了疲劳本构关系的正确性;最后,对某实际钢筋混凝土桥面板进行疲劳数值分析与疲劳寿命预测。结果表明：该桥面板的抗疲劳寿命满足要求;所建立的材料疲劳本构关系能够有效模拟钢筋和混凝土在循环加载过程中力学性能的衰减规律。     

重型矿用汽车车架的疲劳寿命计算

介绍了一种用于重型矿用汽车车架疲劳寿命计算的实用方法。这种方法把随机载荷下的疲劳寿命直接与描述一个应力历程的有关统计参量联系在一起,在对车架进行疲劳寿命计算时,只要求知道常幅应力-寿命数据和车架所经受的应力历程的标准离差与度规频率。用这种方法对我国某矿山使用的重型矿用汽车车架进行了疲劳寿命计算,计算结果与实际情况比较吻合。     

Cold performance of various biodiesel fuel blends at low temperature

This study examines the cold performance of biodiesel blends in a passenger car and a light duty truck at −16 °C and −20 °C. Six different types of biodiesels derived from soybean oil, waste cooking oil, rapeseed oil, cottonseed oil, palm oil and jatropha oil were blended with different volume ratios (B5 (5 vol. % biodiesel — 95 vol. % diesel), B10 and B20). The cold filter plugging point (CFPP) and the cloud point had an effect on the startability and driveability of both the passenger car and the light duty truck. The startability and driveability of the passenger car with all biodiesel blends (B5) were generally good at −20 °C. In the light duty truck, biodiesel blends (B10 and B20) of soybean, waste cooking, rapeseed and jatropha tended to be good at −20 °C in the startability and driveability tests than the biodiesel blends (B10 and B20) of cottonseed and palm. In particular, the palm biodiesel blend (B10) failed at −20 °C, and the palm biodiesel blend (B20) also failed at −16 °C in the startability test. The cold flow properties of biodiesel dictate that the length of the hydrocarbon chains and the presence of unsaturated structures significantly affect the low temperature properties of biodiesel.     

基于洞壁实测信息的FA-PP岩爆预测模型应用研究

为了给岩爆隧道提供更加符合现场实际规律的岩爆预测结果,针对岩爆预测评价中应力判据界限值的多样性以及单一判据预测结果准确性低的特点,提出采用投影寻踪（PP）与萤火虫算法相结合的方法进行岩爆预测评价,解决了岩爆预测中采用多种应力判据时多项指标的模糊性和不兼容性等问题。此方法根据岩爆等级划分标准,构建了以实测数据、现场岩爆信息为基础的能够根据各项指标判定岩爆等级的投影指标函数,选取σ_θ/R_c,σ_t,σ₁三个岩爆评价中常用的指标,并采用萤火虫算法（FA）优化投影指标函数,寻求投影指标函数的最佳投影方向并求得最佳投影值,保证了此方法的精确性。研究结果表明：采用萤火虫投影寻踪算法（FA-PP）进行岩爆等级预测可避免传统预测方法中由于主观原因造成的误差,判定精度高,也免去了利用多项判定指标与现场实际情况进行对比而选择一个相对接近实际情况判据的繁杂过程;此方法可利用目标隧道的已知岩爆发生信息掌握其岩爆发生特点及对3个评价指标的敏感度,构建出符合目标隧道岩爆发生规律的FA-PP岩爆预测模型;以拉林铁路桑珠岭隧道为研究对象,将此方法应用到岩爆预测中,得到的预测结果与现场实测结果较为符合,验证了该方法的可靠性。     

用能量法分析钢桥面沥青混合料铺装体系疲劳特性

介绍了沥青混合料的滞后回路方程和能耗分析方法,并用能量法分析了钢桥面沥青混合料铺装体系疲劳特性, 提出了疲劳寿命预测公式。通过南京长江第二大桥钢桥面铺装体系疲劳试验结果的实例分析,表明能量法可用于分析钢桥面沥青混合料铺装体系疲劳特性,其疲劳寿命预测结果是较为精确的,而且指出了环氧沥青混凝土铺装具有很好的抗疲劳性能。     

增压器涡轮轮毂疲劳可靠性分析与寿命预测方法

针对增压器涡轮由离心载荷所引起的轮毂疲劳失效模式,基于装甲车辆柴油机耐久性台架考核试验剖面,分析了增压器在不同工况下运行时涡轮转速的变化规律,计算了涡轮轮毂疲劳危险部位的应力历程.通过对涡轮轮毂疲劳强度模拟试验样件的疲劳性能测试,建立了涡轮轮毂疲劳寿命与应力之间的数学模型.在此基础上,研究了涡轮轮毂的疲劳可靠性分析与寿...     

西藏高寒地区沥青路面防水防裂设计及疲劳寿命评价

采用剪切、拉拔试验确定了粘层油选型和最佳用量,通过渗水试验、MTS疲劳试验、MMLS3加速加载试验等评价了路面的防裂效果,并对温度和荷载作用进行有限元分析。结果表明:采用1.1~1.3 kg/m2的90-A级沥青作为粘层油最佳,MTS试验加载至完全开裂时,铺设基布的次数是未铺基布的2.64倍,MMLS3试验加载60万次时,层底微应变仅为不铺基布方案的12.22%,有限元分析得出铺设防裂基布使层底应变降低28.38%,实体工程调查显示防裂基布使裂缝率降低了65.29%。铺设防裂基布后形成防水防裂应力吸收层,有助于延缓反射裂缝的发生,延长路面疲劳寿命。     

三种沥青混合料四点弯曲疲劳试验机的对比

采用ASTME1301-95标准,对amesCox＆Sons、COOPERSD IPC沥青混合料疲劳试验机进行了对比研究。沥青混合料初始弯曲劲度模量、疲劳寿命的试验结果及疲劳寿命的回归方程结果表明,上述三种四点弯曲疲劳试验机的试验结果具有较好的一致性：同时指出了应重视沥青混合料疲劳小梁试件的制作工艺与质量对疲劳试验结果的影响。     

Discomfort of vertical whole-body shock-type vibration in the frequency range of 0.5 to 16 Hz

Shock-type vibrations are frequently experienced in vehicles excited by impulsive input, such as bumps in the road, and cause discomfort. Current national and international standard weightings were primarily developed for assessing exposure to sinusoidal or random vibrations and not impulsive excitations or shocks. In this experimental study, various shock signals were systematically produced using the response of a one degree-of-freedom vibration model to hanning-windowed half-sine force input. The fundamental frequency of the shock was varied from 0.5 to 16 Hz at a step of 1/3 of an octave. The magnitude estimation method was used for fifteen subjects to compare the discomfort of shocks with various unweighted vibration dose values between 0.35 ms^−1.75 and 2.89 ms^−1.75 at each frequency. The equivalent comfort magnitude of shock showed greater sensitivity at frequencies less than 0.63 Hz and at the resonance frequency of the human body between 5.0 Hz and 6.3 Hz. The frequency weighting constructed by using both the equivalent comfort magnitude and the growth rate of discomfort obtained in this study was compared with the current standard weightings, W_b of BS 6841 and W_k of ISO 2631. The derived weightings for shock were applied to the acceleration of the shocks, and an enhanced correlation was proved between the magnitude estimations and the weighted physical magnitude of shock.     

Simulation of the vertical bending fatigue test of a five-link rear axle housing

This study seeks a practical method for simulating the vertical bending fatigue test of the BANJO housing of a five-link rear axle. Linear static and transient dynamic finite element models are constructed for the rear axle in which the rubber bushings and the bearings of the axle shafts are reasonably modeled with solid and shell elements, respectively, for simplicity. The calculated results are compared with the measured strain histories, and the results indicate that the finite element models constructed are reasonable. The hypothesis of equal fatigue damage is applied to determine the Hainan proving ground driving life prediction that is equivalent to the constant amplitude fatigue life in the vertical bending fatigue test.     

不同腐蚀率下钢筋混凝土梁的疲劳S-N曲线研究

钢筋混凝土梁中钢筋腐蚀对疲劳的影响不容忽视,针对目前不同腐蚀下钢筋混凝土梁疲劳性能研究较少的情况,介绍了4种疲劳寿命评估方法,并以名义应力疲劳寿命评估法为理论基础,对国内以前做的部分钢筋混凝土梁疲劳试验结果进行了分析,采用应力幅作为钢筋混凝土梁的疲劳参数,取保证概率为95%,拟合了4种不同腐蚀下钢筋混凝土梁的疲劳S-N曲线,并进行对比分析,可为相关研究提供一定的参考。     

Development of active front wheel steering control system keeping stable region in driving phase diagram

This paper presents a new active steering control system based on driving phase diagram (β _fr ?δ _f diagram). In order to make state variables to follow those of nominal vehicle model that was developed under no consideration of disturbance, Quadratic Programming Problem (QPP) is formulated, where time varying objective function minimizes the differences between nominal and actual parameters. The steering characteristic in active steering control system changes when the vehicle faces disturbance such as crosswind and flat tire, and driver tries to counteract it after recognizing the change. The proposed method defines a stability region on β _fr ?δ _f diagram. In order to make β _fr and δ _f remain in the stability region, a new model predictive controller is proposed. While conventional controllers are restrictive to satisfy the β _fr ?δ _f diagram based stability condition, the proposed controller ensures solution space and also plays a direct role to minimize the evaluation function in the constrained optimal control problem.     

车载电子电器零件常用加速试验及可靠性计算方法

简要介绍电子电器零件结合环境应力的寿命加速模型,以及可靠性试验要求的计算方法。首先介绍了3种加速模型,以及其相应的应用情况;其次,根据给定的可靠度、置信度水平计算相应的可靠性测试要求;最后根据实际的测试结果,得到产品的实际可靠度,并以此来指导设计。