考虑岩石抗拉强度受围压影响的地层破裂压模型

预测地层破裂压力是地下流体注入工程中的关键问题，关系到工程的稳定性和安全性。根据地测资料，岩石的抗拉强度会随着围压产生变化，然而目前常见的地层破裂压预测模型均未考虑该因素。基于厚壁圆筒法，针对2种砂岩开展不同围压条件下的砂岩致裂试验，根据试验数据，计算各组试验中试样的抗拉强度，并拟合围压与岩石抗拉强度的关系函数。研究岩石抗拉强度随围压变化的规律，提出能在实际地层中表征该规律的参数，基于该参数对现有的地层破裂压模型进行修正，并结合实测数据验证修正模型的可靠性。研究结果表明:岩石的抗拉强度随着围压的增加呈现明显的线性正相关关系，低围压下，新模型的预测结果与实测数据较为接近。随着围压增加，二者的差异逐渐增大，说明选取的特征参数在低围压下能较好地描述抗拉强度受围压的影响效应，而高围压下参数的取值需进一步研究。     

基于RFPA2D复合局部挠曲岩体数值模拟

为研究复合局部挠曲岩体强度特征以及破坏规律，采用岩石真实破裂软件RFPA^2D，对水平层面挠曲30°，45°，60°，75°的复合岩体进行单轴压缩试验模拟。模拟结果表明:挠曲角为30°，45°，60°，75°的复合岩体破坏面几乎与挠曲段夹层重合，其挠曲端部均产生了垂直于挠曲段夹层的裂纹；复合单斜岩体与复合挠曲岩体破坏面的形成因素大致相同，夹层强度是2种岩体失稳的主要因素；复合挠曲岩体单轴抗压强度随挠曲角增大同样呈“U”型变化，与单斜岩体变化趋势一致；当水平层状岩体发生挠曲后，其单轴抗压强度减小，当挠曲角为60°时，强度降低25.19%，当挠曲角为75°时，强度降低0.17%。；随着均质系数m的增大，复合挠曲岩体单轴抗压强度以及轴向应变均出现逐渐递增的趋势，且不同m值，其岩体裂隙扩展方式具有明显差别。     

游梁式抽油机底座断裂故障分析

对一起游梁式抽油机底座断裂故障进行了原因分析,并根据具体原因提出了相应的防范措施,以减少此类故障的发生概率,确保抽油机安全平稳运行。     

四川红层浅层风化带裂隙水水化学特征的聚类分析

四川红层盆地浅层风化带裂隙水是区内分布最为广泛和目前开采最多的浅层地下水类型,本文通过对大量控制性水样分析结果进行聚类分析,探讨了该地区浅层风化带裂隙水的水化学成分特征及其分布规律,结果表明区内91%以上的浅层风化带裂隙水为HCO3-型淡水,主要分布在中部方山丘陵小区、南部台状低山丘陵小区和东部侵蚀构造平行岭谷低山丘陵小区。该研究可为开发利用浅层地下水提供地学依据。     

反应器引压端法兰焊接阀门断裂原因分析

通过对Z41H-160型阀体端法兰断裂件的宏观检查、化学成分分析、金相分析、断口形貌观察、EDS能谱分析和维氏硬度测试等研究,表明阀体热处理不当致使硬度超高,阀门结构不合理导致硫化物应力腐蚀是阀体断裂的主要原因。     

热采卡箍螺拴断裂事故原因分析

在对发生断裂的卡箍紧固连接螺栓进行质量检测和强度校核的基础上,指出螺栓发生断裂的主要原因是预紧力太大,并提出了相应的整改措施,解决了工程中存在的问题.     

弹丸壳体和身管破坏效应仿真

为了研究膛炸时弹丸壳体和身管的破坏效应,用双层金属圆管代替弹丸壳体和身管建立了简易膛炸模型,并运用LS-DYNA动力有限元程序对膛炸过程仿真,分别采取不同的装药方式和起爆方式进行了模拟.仿真结果表明,在不同的装药方式和起爆方式下,弹丸和身管破坏过程及最终破坏效果存在差异.采用的仿真方法和得到的结果可为进一步研究诸如发射...     

煤与瓦斯突出过程中煤体层裂演化特征实验研究

为了探究煤与瓦斯突出过程中煤体层裂演化特征,利用自主研制的煤与瓦斯突出实验模拟系统,研究突出过程中煤体层裂结构特征、煤体裂隙厚度演化特征和煤体质点运动演化特征。研究结果表明:在轴向应力0.9 MPa、瓦斯压力0.4 MPa时,煤体层裂发展时间持续85 ms,煤体共计出现11处裂隙。层裂从煤体后方的弱构面出现并向前方发展,其位置大多集中于突出腔体中后部,煤体层裂形式均为纵向贯通,在第9处出现最大纵向断裂裂隙。煤体裂隙总厚度约为75.6 mm、单处裂隙平均厚度约为8.4 mm,二者均呈现随时间递增的趋势。层裂过程中煤体单处裂隙厚度并不都是沿程递增的,部分煤体中部裂隙厚度呈现先增大后减小的特征。煤体的运动表现为靠近突出口端的运动速度更快、运动距离也更长。研究结果可为揭示煤与瓦斯突出层裂机制提供参考。     

Injuries in Full-Scale Vehicle Side Impact Moving Deformable Barrier and Pole Tests Using Postmortem Human Subjects

Objective: To conduct near-side moving deformable barrier (MDB) and pole tests with postmortem human subjects (PMHS) in full-scale modern vehicles, document and score injuries, and examine the potential for angled chest loading in these tests to serve as a data set for dummy biofidelity evaluations and computational modeling.

Methods: Two PMHS (outboard left front and rear seat occupants) for MDB and one PMHS (outboard left front seat occupant) for pole tests were used. Both tests used sedan-type vehicles from same manufacturer with side airbags. Pretest x-ray and computed tomography (CT) images were obtained. Three-point belt-restrained surrogates were positioned in respective outboard seats. Accelerometers were secured to T1, T6, and T12 spines; sternum and pelvis; seat tracks; floor; center of gravity; and MDB. Load cells were used on the pole. Biomechanical data were gathered at 20 kHz. Outboard and inboard high-speed cameras were used for kinematics. X-rays and CT images were taken and autopsy was done following the test. The Abbreviated Injury Scale (AIS) 2005 scoring scheme was used to score injuries.

Results: MDB test: male (front seat) and female (rear seat) PMHS occupant demographics: 52 and 57 years, 177 and 166 cm stature, 78 and 65 kg total body mass. Demographics of the PMHS occupant in the pole test: male, 26 years, 179 cm stature, and 84 kg total body mass. Front seat PMHS in MDB test: 6 near-side rib fractures (AIS = 3): 160–265 mm vertically from suprasternal notch and 40–80 mm circumferentially from center of sternum. Left rear seat PMHS responded with multiple bilateral rib fractures: 9 on the near side and 5 on the contralateral side (AIS = 3). One rib fractured twice. On the near and contralateral sides, fractures were 30–210 and 20–105 mm vertically from the suprasternal notch and 90–200 and 55–135 mm circumferentially from the center of sternum. A fracture of the left intertrochanteric crest occurred (AIS = 3). Pole test PMHS had one near-side third rib fracture. Thoracic accelerations of the 2 occupants were different in the MDB test. Though both occupants sustained positive and negative x-accelerations to the sternum, peak magnitudes and relative changes were greater for the rear than the front seat occupant. Magnitudes of the thoracic and sternum accelerations were lower in the pole test.

Conclusions: This is the first study to use PMHS occupants in MDB and pole tests in the same recent model year vehicles with side airbag and head curtain restraints. Injuries to the unilateral thorax for the front seat PMHS in contrast to the bilateral thorax and hip for the rear seat occupant in the MDB test indicate the effects of impact on the seating location and restraint system. Posterolateral locations of fractures to the front seat PMHS are attributed to constrained kinematics of occupant interaction with torso side airbag restraint system. Angled loading to the rear seat occupant from coupled sagittal and coronal accelerations of the sternum representing anterior thorax loading contributed to bilateral fractures. Inward bending initiated by the distal femur complex resulting in adduction of ipsilateral lower extremity resulted in intertrochanteric fracture to the rear seat occupant. These results serve as a data set for evaluating the biofidelity of the WorldSID and federalized side impact dummies and assist in validating human body computational models, which are increasingly used in crashworthiness studies.     

Lower Leg Injury Reference Values and Risk Curves from Survival Analysis for Male and Female Dummies: Meta-analysis of Postmortem Human Subject Tests

Objective: Derive lower leg injury risk functions using survival analysis and determine injury reference values (IRV) applicable to human mid-size male and small-size female anthropometries by conducting a meta-analysis of experimental data from different studies under axial impact loading to the foot–ankle–leg complex.

Methods: Specimen-specific dynamic peak force, age, total body mass, and injury data were obtained from tests conducted by applying the external load to the dorsal surface of the foot of postmortem human subject (PMHS) foot–ankle–leg preparations. Calcaneus and/or tibia injuries, alone or in combination and with/without involvement of adjacent articular complexes, were included in the injury group. Injury and noninjury tests were included. Maximum axial loads recorded by a load cell attached to the proximal end of the preparation were used. Data were analyzed by treating force as the primary variable. Age was considered as the covariate. Data were censored based on the number of tests conducted on each specimen and whether it remained intact or sustained injury; that is, right, left, and interval censoring. The best fits from different distributions were based on the Akaike information criterion; mean and plus and minus 95% confidence intervals were obtained; and normalized confidence interval sizes (quality indices) were determined at 5, 10, 25, and 50% risk levels. The normalization was based on the mean curve. Using human-equivalent age as 45 years, data were normalized and risk curves were developed for the 50th and 5th percentile human size of the dummies.

Results: Out of the available 114 tests (76 fracture and 38 no injury) from 5 groups of experiments, survival analysis was carried out using 3 groups consisting of 62 tests (35 fracture and 27 no injury). Peak forces associated with 4 specific risk levels at 25, 45, and 65 years of age are given along with probability curves (mean and plus and minus 95% confidence intervals) for PMHS and normalized data applicable to male and female dummies. Quality indices increased (less tightness-of-fit) with decreasing age and risk level for all age groups and these data are given for all chosen risk levels.

Conclusions: These PMHS-based probability distributions at different ages using information from different groups of researchers constituting the largest body of data can be used as human tolerances to lower leg injury from axial loading. Decreasing quality indices (increasing index value) at lower probabilities suggest the need for additional tests. The anthropometry-specific mid-size male and small-size female mean human risk curves along with plus and minus 95% confidence intervals from survival analysis and associated IRV data can be used as a first step in studies aimed at advancing occupant safety in automotive and other environments.