Effect of Seasonal Variations on the Behavior of Flexible Pavements in Burkina Faso: Towards Alternating and Periodic Loading of Multi-Axle Heavy Goods Vehicles for Road Durability

Bituminous materials are heat-sensitive, and their mechanical properties vary with temperature. This variation in properties is not without consequences on the performance of flexible road structures under the repeated passage of multi-axles. This study determines the influence of seasonal variations on the rate of permanent deformation, the rut depth of flexible pavements and the effect of alternating loading of heavy goods vehicles following the temperature variations on the durability of roads. Thus, an ambient and pavement surface temperature measurement was carried out in 2022. The temperature profile at different layers of the modelled pavement, the evaluation of deformation rates and rutting depth were determined using several models. The results show that the permanent deformation and rutting rates are higher at the level of the bituminous concrete layer than at the level of the asphalt gravel layer because the stresses decrease from the surface to the depth of the pavement. On the other hand, the variations in these rates, permanent deformations and ruts between the hot and so-called cold periods are more pronounced in the bitumen gravel than in bituminous concrete, showing that gravel bitumen is more sensitive to temperature variations than bituminous concrete despite its higher rigidity. Of these results, we suggested a periodic and alternating loading of the different types of heavy goods vehicles. These loads consist of fully applying the WAEMU standards with a tolerance of 15% during periods of high and low temperatures. This regulation has increased 2 to 3 times in the durability of roadways depending on the type of heavy goods vehicle.

High Temperature Rheological Performance of Graphene Modified Rubber Asphalt

To elucidate the high temperature rheological capability of graphene modified rubber asphalt,three contents of graphene and crumb rubber were prepared by a combination of mechanical agitation and high speed shearing machine,then used dynamic shear rheological test(DSR)and multiple stress creep recovery(MSCR)tests to evaluate.The hardness and softening point with rotational viscosity of samples raised with the addition of graphene,especially the addition of 0.04%.Dynamic shear rheological test revealedthat the dynamic shear modulus G*,rutting factor G*/Sin δ,and zero shear viscosity(ZSV)of graphene-modified rubber asphalt were greatly influenced along with graphene-increased,on the contrary,phase angle δ which characterize the viscoelastic ratio of asphalt decreased.Multiple stress creep recovery(MSCR)tests showed that the graphene-enhanced rubber asphalt had high-temperature stability through non-recoverable creep compliance(Jnr).Based on these findings,graphene-modified rubber asphalt binders with the addition of 0.04% graphene had good viscoelastic properties as well as high temperature rutting resistance performance.In the meantime,G*/Sin δ,ZSV,and Jnr100,Jnr3200 have good correlation,which can reveal the excellent high-temperature stability performance of asphalt.

微织构铣刀干铣削RuT500切削性能研究

为探究微织构对刀具加工蠕墨铸铁RuT500切削性能的影响,改善RuT500的可加工性,利用激光技术在刀具前刀面制备了3种形式的微织构并通过单因素试验方法,在不同切削速度下将微织构刀具和无织构刀具对RuT500进行铣削加工,对比分析了微织构的方向和类型在加工中切削性能的差异。结果表明,表面微织构可以有效降低切削力,改善切屑形态和工件表面质量,在一定程度上降低了前刀面磨损;3种微织构在部分相同切削速度下对切削性能的影响有较大差别;切削速度较大时,微织构更有利于RuT500的切削加工。在3种微织构中,以平行于主切削刃的沟槽织构刀具切削性能最优。

RuT450气缸盖铸造工艺的研究

根据RuT450柴油机气缸盖的技术要求确定了铸造工艺,通过MAGMA软件对充型、凝固及缺陷等进行分析,验证铸造工艺的可行性。采用铸件浇注后在砂型内延缓开箱时间,在箱内缓慢冷却的免退火处理工艺,铸件的残余应力小于40 MPa,同时铸件的力学性能和组织均满足技术要求。

复合涂层刀具加工RuT500的铣削力研究及参数优化

为探究和改善蠕墨铸铁RuT500的铣削力,基于单因素试验,选用TiAlN/AlCrN、TiCN/Al_(2)O_(3)复合涂层硬质合金刀具对RuT500进行铣削加工,结合响应面探究涂层和铣削参数对RuT500铣削力的影响规律,并进行了铣削参数优化。结果表明:相比于TiAlN/AlCrN复合涂层硬质合金刀具,TiCN/Al_(2)O_(3)复合涂层硬质合金刀具铣削RuT500时会产生更大的铣削力;对蠕墨铸铁铣削力影响最显著的因素是背吃刀量,其次是进给量,铣削速度对蠕墨铸铁铣削力的影响程度相对较少;铣削参数交互作用对铣削力的影响具有一定的显著性;取较大的背吃刀量a_(p)、适当的进给量f和较大的铣削速度v_(c)时,可以获得较低的铣削力F和良好的加工效率。

提升柴油机气缸盖内腔质量的工艺措施

针对柴油机气缸盖铸件内腔的披缝和烧结缺陷问题,分析认为气缸盖内腔的水套砂芯形状复杂、砂芯的配合面多且壁厚偏薄是产生缺陷的主要原因。通过在模具上提升模拟射砂仿真技术、优化射砂嘴结构、引进电火花技术;并调整制芯工艺解决了缺陷问题,批量生产出合格铸件。

The Influence of Mesoscopic Characteristics of Mineral Powders Fillers on the Rutting Factor(G^(*)/sinδ)of Asphalt Mortar

This study aims to investigate the efiect of the mesoscopic characteristics of mineral powder fillers on the rutting resistance of asphalt mortar.Extraction and sieving tests were used to obtain the buton rock asphalt(BRA)ash with particle size smaller than 0.075 mm,which is consistent with that of the conventional mineral powder.The mesoscopic characteristics of BRA ash and conventional mineral powder were measured by SEM image analysis and the osmotic free pressure water method.Mesoscopic structure models of structural and free asphalts in mortar were obtained.The 70#matrix asphalt was used to prepare two kinds of asphalt mortar with BRA ash and conventional mineral powders fillers.The rutting factor of the two asphalt mortars was tested by dynamic shear test(DSR).Test results show that the ash extracted from BRA has a similar mesoscopic classification with the conventional mineral powder.Still,its fractal dimensions are larger,indicating the particles in BRA ash have more complex shapes and rougher surfaces,which is beneficial for forming structural asphalt and subsequently increasing the rutting factor(G*/sinδ),i e,improving the rutting resistance of the asphalt mortar.

A Data-Driven Rutting Depth Short-Time Prediction Model With Metaheuristic Optimization for Asphalt Pavements Based on RIOHTrack

Rutting of asphalt pavements is a crucial design criterion in various pavement design guides. A good road transportation base can provide security for the transportation of oil and gas in road transportation. This study attempts to develop a robust artificial intelligence model to estimate different asphalt pavements’ rutting depth clips, temperature, and load axes as primary characteristics. The experiment data were obtained from19 asphalt pavements with different crude oil sources on a 2.038km long full-scale field accelerated pavement test track(Road Track Institute, RIOHTrack) in Tongzhou, Beijing. In addition,this paper also proposes to build complex networks with different pavement rutting depths through complex network methods and the Louvain algorithm for community detection. The most critical structural elements can be selected from different asphalt pavement rutting data, and similar structural elements can be found. An extreme learning machine algorithm with residual correction(RELM) is designed and optimized using an independent adaptive particle swarm algorithm. The experimental results of the proposed method are compared with several classical machine learning algorithms, with predictions of average root mean squared error(MSE), average mean absolute error(MAE), and a verage mean absolute percentage error(MAPE) for 19 asphalt pavements reaching 1.742, 1.363, and 1.94% respectively. The experiments demonstrate that the RELM algorithm has an advantage over classical machine learning methods in dealing with non-linear problems in road engineering. Notably, the method ensures the adaptation of the simulated environment to different levels of abstraction through the cognitive analysis of the production environment parameters. It is a promising alternative method that facilitates the rapid assessment of pavement conditions and could be applied in the future to production processes in the oil and gas industry.

Analytical Study on the Effect of Electric Arc Furnace Dust(EAFD)on the Rutting of Asphalt Concrete Mixtures

As a byproduct of the steelmaking process,significant amounts of hazardous electric arc furnace dust(EAFD)are produced.Utilizing the solidification/stabilization technology with asphalt mix is one way to safeguard the environment from its negative effects.Rutting was used as an indicator to assess the asphalt mixture with EAFD since it is an important factor in pavement design.This study’s major goal is to ascertain how EAFD affects the rutting of asphalt-concrete mixtures.To evaluate the ideal asphalt content,the Marshall test method was applied to asphalt-concrete mixtures.EAFD was added to the asphalt cement in four different volume percentages as a binder addition.Then,using the Universal Testing Machine,participants were exposed to a replica of the rutting test(UTM).Experiments were conducted at 25℃,40℃ and 55℃,and at frequencies of 1 Hz,4 Hz and 8 Hz.Rutting was measured for each specimen.Test results showed that rut depth has a negative correlation with EAFD%and a positive correlation with temperature.The use of EAFD has dual advantages,protecting the environment from the adverse impact of EAFD and reducing the cost of asphalt mix without jeopardizing pavement performance.

热处理工艺对RuT300蠕墨铸铁力学性能与导热性能的影响

对Ru T300蠕墨铸铁合金进行了900℃、950℃、1000℃正火处理,并对1000℃加热处理的试样进行不同冷却处理(炉冷,空冷,风冷和喷水雾冷)。与铸态合金相比,热处理后的Ru T300蠕墨铸铁合金中珠光体含量随奥氏体化加热温度提高而增高。并且随着奥氏体化后冷却速度的增大,珠光体含量逐渐增高,最高可达77.6%,较铸态组织增加了50%,珠光体层片间距逐渐减小,最小间距约为0.2μm,较铸态珠光体减小了0.4μm,抗拉强度和布氏硬度分别提高了25%和73%,但导热性能下降20%~30%。热处理后蠕虫状石墨数量和尺寸有所减小(1000℃),石墨与基体结合部位会出现开裂、脱粘现象,导致传热受阻,导热率下降。

里氏木霉Rut—30产纤维素酶发酵条件的优化

采用单因素试验、正交试验设计对产纤维素酶的里氏木霉RutC—30菌株进行了液体摇瓶发酵条件优化实验。结果表明,在pH为4.8、每50 mL发酵液接种2.5 mL菌种时,里氏木霉RutC—30菌株产酶发酵最优培养条件是:工业纤维素30 g/L、(NH4)2SO412 g/L、Mandels营养盐浓缩液125 mL/L。在此条件下,发酵产生的纤维素酶滤纸酶活达到4.845 U.m L-1,相对于微晶纤维素碳源提高了49.6%。同时,在本实验中还发现里氏木霉RutC—30菌株的生长与产酶存在着偶联性。通过优化实验,里氏木霉RutC—30菌株达到了比较高的产纤维素酶能力,为纤维素酶进一步工业化生产奠定了一定基础。

以太网分布式测试系统中实时传输技术研究

介绍了分布式测试系统中通信的特点;分析交换式以太网的工作方式及以太网中端到端延时的因素;针对测试系统中实时传输的要求,利用UDP传输的高效性,提出一种基于UDP用于测试领域的可靠传输协议RUT(Reliable UDP for Test System);通过设置接收缓冲区,发送缓冲区,以及对发送的数据进行确认等措施,保证数据在测试网络中可靠传输;经过测试该传输协议具有较好实时性和可靠性,并应用于工业测控领域。

Rutting resistance of asphalt mixtures in the middle course

In order to improve the rutting resistance of asphalt mixtures in the middle course to reduce the rutting of asphalt pavement, the influence of different types of gradation with their own optimal asphaltaggregate ratios is analyzed. Some investigations are made out on the mixture in the middle course through the modified wheel tracking test in air bath and the Hamburg wheel tracking test （HWTT） in water bath, and the results of which are compared with the corresponding research in Germany. Results show that the Sup20 and the modified AC-20I have better performance than that of AC-20I under the same test conditions. In addition, the high-quality bitumen and hard aggregate can improve the rutting performance of the mixture in water-submerged conditions. The selection of modified asphalt, hard aggregate and a reasonable gradation are essential to the improvement of the rutting resistance of the mixtures used in the middle course.

Asphalt pavement short-term rutting analysis and prediction considering temperature and traffic loading conditions

The rutting simulation method considering temperature variance and traffic time distribution is developed through ABAQUS software. The short-term behavior of pavement rut under the effects of temperature and traffic loading is addressed. Then sensitivity analysis on the factors of temperature and traffic loading is conducted and a short-term rutting prediction model is developed. The results show that under the same conditions of temperature and the number of load repetitions, rut increases sharply with the contact pressure in a linear manner, while as for the heavy load situation, the increases likely to be more nonlinear and faster; the significant factors affecting rutting include daily maximum air temperature, daily solar radiation volume, daily minimum air temperature, tire-pavement contact pressure and the number of load repetitions. Finally, a short-term rutting prediction model reflecting the effects of air temperature and traffic loading is developed, and it can be used for prediction and pre-waming for pavement rut prevention.

Prediction method of highway pavement rutting based on the grey theory

In order to make a scientific pavement maintenance decision, a grey-theory-based prediction methodological framework is proposed to predict pavement performance. Based on the field pavement rutting data,analysis of variance （ANOVA）was first used to study the influence of different factors on pavement rutting. Cluster analysis was then employed to investigate the rutting development trend.Based on the clustering results,the grey theory was applied to build pavement rutting models for each cluster, which can effectively reduce the complexity of the predictive model.The results show that axial load and asphalt binder type play important roles in rutting development.The prediction model is capable of capturing the uncertainty in the pavement performance prediction process and can meet the requirements of highway pavement maintenance,and,therefore,has a wide application prospects.

Virtual rutting test of asphalt mixture using discrete element method

In order to investigate the permanent deformation behavior of asphalt mixtures from discontinuity, the virtual rutting test of asphalt mixtures is developed by the discrete element method （DEM）. A digital specimen generation procedure considering aggregate gradation and irregular shape is developed based on the probability theory and the Monte Carlo method. The virtual rutting test is then conducted based on the generated digital specimen. In addition, on the basis of the time-temperature superposition （TTS） principle, a calculation method is used to reduce the computation time of the virtual rutting test. The simulation results are compared with the laboratory measurements. The results show that the calculation method based on the TFS principle in the discrete element （DE） viscoelastic model can significantly reduce the computation time. The deformation law of asphalt mixtures in the virtual rutting test is similar to the laboratory measurements, and the deformation and the dynamic stability of the virtual rutting test are slightly greater than the laboratory measurements. The two-dimensional virtual rutting test can predict the permanent deformation performance of asphalt mixtures.

RuT300蠕墨铸铁熔炼工艺研究

探讨了RuT300蠕墨铸铁在12 kg中频感应电炉中的熔炼工艺。采用FeSiMg5RE5蠕化剂,硅钡合金孕育剂,以及凹坑法蠕化处理工艺,研究了蠕化剂加入量、出铁温度及蠕化时间对蠕化率的影响。实验得出最佳的熔炼工艺为:蠕化剂加入量为0.65%,出铁温度为1 560℃,蠕化时间为25 s。

幽门螺杆菌口腔唾液测试板的临床应用价值

目的探讨唾液幽门螺杆菌(H.pylori)测试板(HPS)检测H.pylori感染的临床价值。方法对228例无明显消化道症状行胃镜检查的体检者进行HPS检测及快速尿素酶试验,175例同时行病理HE染色检测,146例同时行结肠镜检查,对结果进行分析。结果 1HPS与联合检测(RUT或病理HE染色)相比较,阳性检出率分别为47.8%、41.67%,阳性符合率(灵敏度)为84.2%,阴性符合率(特异度)为78.2%,准确率为75.4%,阳性预测值为73.4%,阴性预测值为87.4%;HPS与HE染色检测相比较,阳性检出率分别为47.8%、40%,灵敏度为85.7%,特异度为68.7%,准确率为75.4%,阳性预测值为64.5%,阴性预测值为87.8%;与RUT方法比较,灵敏度为88.7%,特异度为67.5%,准确率为73.2%,阳性预测值为50.5%,阴性预测值为94.1%。2行胃黏膜活检的175例中,病理分别诊断为萎缩、糜烂、胃息肉、肠上皮化生及不典型增生的病例,H.pylori感染均有着较高的检出率。对结果进行卡方检验,萎缩、肠上皮化生及不典型增生中,HPS与HE染色阳性检出率的差异有统计学意义。3146例同时接受了结肠镜检查,发现息肉的78例中,HPS、HE染色的阳性率分别为69.2%、45.4%,差异有统计学意义。息肉行内镜下切除后诊断为腺瘤性息肉的24例,对应HPS、HE染色的阳性率为66.7%、47.4%。结论 HPS具有操作简单、快速、无痛苦等优点。是临床筛查H.pylori感染的一种很有价值的非侵入性方法,值得临床进一步验证。同时,HPS对萎缩、腺瘤性息肉等癌前病变的筛查可能具有一定的价值。

里氏木霉以稻草和麸皮为基质产木聚糖酶的研究

以稻草和麸皮为主要基质,对里氏木霉RutC-30产木聚糖酶的固体发酵条件进行研究。试验表明:固态发酵培养基中添加麸皮不利于产木聚糖酶,最适氮源为(NH4)2SO4,干料与水分的比例为1∶3·5,并分析了无机盐对里氏木霉RutC-30产木聚糖酶的影响:MgSO4·7H2O>MnSO4·H2O>ZnSO4·H2O>FeSO4·7H2O。酶粗酶液的最适作用pH为4·8,最适反应温度为55℃。

里氏木霉Rut C-30产非淀粉多糖酶发酵条件的研究

在接种量与培养温度分别为8%和30℃条件下,采用正交试验表L9(34)设计对培养基组成、发酵时间、培养基湿度和发酵容器4个试验因子进行产酶影响力排序和条件组合优化,同时分析各指标间相关性。结果:对纤维素酶,培养基组成>发酵时间>发酵容器>初始湿度,最优组合酶活力456.3u/g;对木聚糖酶,发酵时间>培养基组成>发酵容器>初始湿度,最优组合酶活力5529.9u/g;对β-甘露聚糖酶,发酵容器>培养基组成>初始湿度>发酵时间,优化组合酶活力367.6u/g;对果胶酶,培养基组成>发酵容器>发酵时间>初始湿度,最优组合酶活力为544.6u/g;培养基发酵失重与β-甘露聚糖酶活力极显著正相关(r=0.811,P<0.01)、纤维素酶与木聚糖酶活力显著正相关(r=0.724,P<0.05)。结论:通过改变发酵条件可调控该菌株产饲用NSP酶谱的酶活水平与比例,指标之间相关性可用于监测发酵过程中的酶活力状态。该菌株较适合作为饲用NSP复合酶制剂生产的菌株。