Assessing cutter-rock interaction during TBM tunnelling in granite:Large-scale standing rotary cutting tests and 3D DEM simulations

The widespread utilisation of tunnel boring machines(TBMs)in underground construction engineering requires a detailed investigation of the cutter-rock interaction.In this paper,we conduct a series of largescale standing rotary cutting tests on granite in conjunction with high-fidelity numerical simulations based on a particle-type discrete element method(DEM)to explore the effects of key cutting parameters on the TBM cutter performance and the distribution of cutter-rock contact stresses.The assessment results of cutter performance obtained from the cutting tests and numerical simulations reveal similar dependencies on the key cutting parameters.More specifically,the normal and rolling forces exhibit a positive correlation with penetration but are slightly influenced by the cutting radius.In contrast,the side force decreases as the cutting radius increases.Additionally,the side force shows a positive relationship with the penetration for smaller cutting radii but tends to become negative as the cutting radius increases.The cutter's relative effectiveness in rock breaking is significantly impacted by the penetration but shows little dependency on the cutting radius.Consequently,an optimal penetration is identified,leading to a low boreability index and specific energy.A combined Hertz-Weibull function is developed to fit the cutter-rock contact stress distribution obtained in DEM simulations,whereby an improved CSM(Colorado School of Mines)model is proposed by replacing the original monotonic cutting force distribution with this combined Hertz-Weibull model.The proposed model outperforms the original CSM model as demonstrated by a comparison of the estimated cutting forces with those from the tests/simulations.The findings from this work that advance our understanding of TBM cutter performance have important implications for improving the efficiency and reliability of TBM tunnelling in granite.

Drag pick cutting tests: A comparison between experimental and theoretical results

This paper aims at reporting the results of a number of drag pick cutting tests on selected igneous rock samples to compare the experimentally determined maximum cutting force （FC） values with theoreti- cally estimated ones. First, a review on theoretical rock cutting models proposed for both chisel and conical picks was presented in detail. Experimental study consists of both chisel and conical pick cutting tests in unrelieved （single-pick） cutting mode with varying cutting depths. FC＇ values were determined from experimental results, and theoretical models were utilized to compute FC for all cutting conditions. Computed and experimentally determined F（ data were then compared for a referenced cutting depth. It is shown that the theoretical models might overestimate or underestimate FC＇ and cannot give reliable results. Finally, explanations for these mismatches were presented.

Design of multi-section luffing apple pruning equipment and cutting test of the key components

In order to reduce the labor intensity and improve the efficiency of pruning,this study designed a multi-section luffing apple pruning equipment suitable for apple orchards in hilly and mountainous areas of China.In the essay,the structure and working principle of the equipment are expounded,the cutter was analyzed,and the parameters were determined.Using the self-made test bench to simulate the field experiment,this study selected the ratio of cutting speed to feeding speed and feeding speed as the influencing factors and took the cut-off rate,cutting efficiency and cutting power as the objectives to carry out single factor experiment and quadratic regression orthogonal experiment.The test results show that the cutting power increases with the increase of ratio of cutting speed to feeding speed,and the cut-off rate and cutting efficiency first increase and then decrease.As the feeding speed increases,the cutting efficiency and power increase,and the cut-off rate decreases.When the cutoff rate was greater than 80%,the optimal combination of operating parameters was the feeding speed of 0.55 m/s and ratio of cutting speed to feeding speed of 1.29.Under this combination,the cut-off rate was 84.9%,the cutting efficiency was 13.1,and the cutting power was 175.7 W.The error between the predicted target value of the model and the average measured target value was less than 7%,so the test results are reliable.According to the obtained optimal operating parameters,the actual cutting experiment of the pruning equipment in the field was carried out,and the cutting rate was 96.3%,which meet the design requirements.This study can also meet the needs of mechanized pruning of fruit trees with different crown shapes,improve the applicability of pruning equipment,and provide support for the development of mechanized pruning equipment in China.

Model test of the cutting properties of a shearer drum

According to similarity theory, we carried out a dimensional analysis of the shearer drum correlation parameters and built similarity criteria. Based on these, similarity models of shearer drums were developed. Simultaneously, based on an estab- lished cutting testbed of the coal and rock, cutting tests of different pick arrangements of the drum models were carried out, where the compressive strength of the analogous cutting material was 2.48 MPa and the drum rotary speed 67.5 r/min. The variance, the mean values, maxima and mean maxima of the torque load were analyzed for different type drum models. Moreover, the relation-ships between the type of pick arrangements and the cutting lump coal percentage were studied. The results indicate that the load fluctuation of the sequence drum is larger than that of the punnett square drum in the cutting process and the lump coal percentage and economic benefits of the sequence drum are inferior to the punnett square drum. We conclude that the punnett square drum is superior to the sequence drum.

Bench cutting tests and analysis for harvesting hemp stalk

As a study basis in the field of design and research of harvester prototype,bench cutting test is to provide best parameters for the cutter design.In order to obtain the optimal parameters of cutter of the hemp harvester,cutting tests on hemp stalk were conducted to examine the influences of different geometrical parameters(length and edge type)of blade,different cutting speeds and stalk feeding speeds of reciprocating single movable blade and reciprocating double movable blades on the cutting performances(cutting power,cutting quality and synthesis score)by using self-designed test bench.According to features of different test factors,multi-factors orthogonal test was applied to determine the best combination of blade length,blade edge type and number of movable blade.Then with these parameters fixed,the optimal parameters for the factors of cutting speed and stalk feeding speed were obtained by quadratic-regression rotatable orthogonal test.According to the test results,the best combination of hemp stalk cutting was that using cutter with reciprocating double movable blades of long(120 mm)and serrated-edge at cutting speed of 1.1704 m/s and stalk feeding speed of 0.7079 m/s.The tests and analysis results can be applied into subsequent related researches on hemp harvesters.

An Experimental Study of Cutting Performance of Ti(C, N) Based Cermet Cutting Tool

Through systematic cutting experiments, characteristics of the cutting performance of Ti(C, N) based cermets is identified. The experiments were designed to study their resistance,toughness, cutting force, tool-chip friction coefficient and machining quality by comparing them with those of WC based cemented carbides. The cutting data and the regressed empirical formulae would be useful to promote proper application of cermet cutting tool materials.

Effects of Fermentation and Drying on the Fermentation Index and Cut Test of Pulp Pre-conditioned Ghanaian Cocoa （Theobroma cacao） Beans

Investigations were conducted to establish effects of fermentation and drying on the fermentation index （FI） and cut test of pulp pre-conditioned Ghanaian cocoa beans using a 4 x 3 full factorial experimental design with the principal factors being pod storage （0, 3, 7 and 10 d） and fermentation time （0, 3 and 6 d） to study the changes occurring during the fermentation process. The study also used a 4 x 3 full factorial design with pod storage （0, 3, 7 and 10 d） and drying time （0, 3 and 7 d） being the principal factors investigated to study the changes occurring during the drying process. FI and cut test of the beans were studied during fermentation as well as the drying process. FI of the beans increased significantly with pod storage and fermentation but decreased slightly during drying. FI of the unfermented beans increased slightly from 0.674 for the unstored pods to 0.763 after 10 days of pod storage. The FI of the fermented beans （six days fermentation） also increased from 1.390 for the unstored pods to 1.424 for pods stored for 10 days. It decreased from 1.389 at the start of drying for the unstored pods to 1.105 for pods stored for 10 days at the end of drying （seven days）. FI of all the beans were however, above 1.0 at the end of fermentation and drying for all pod storage treatments. Cut test revealed that storage of pods for 3, 7 and 10 days increased the percentage of brown beans by 66%, 94% and 72%, respectively, by the sixth day of fermentation. Percentage of brown beans decreased to 61%, 76% and 63%, respectively, for pods stored for 3, 7 and 10 d at the end of drying （seven days）. Cocoa pods can be stored for up to 10 days, fermented for six days and dried for seven days with the necessary formation of brown pigments characteristics of well fermented and dried cocoa beans.

Effect of Al and Si additions on microstructure and mechanical properties of TiN coatings

Ti-X-N (X=Al,Si or Al+Si) coatings were grown onto cemented carbide substrates by cathodic arc evaporation. The hardness of the coatings was obtained by nanoindentation and the microstructure was investigated by XRD,XPS and SEM. Solid solution hardening results in a hardness increase from 24 GPa for TiN to 31.2 GPa for TiAlN. The higher hardness values of 36.7 GPa for TiSiN and 42.4 GPa for TiAlSiN are obtained by the incorporation of Si into TiN (TiAlN) coatings due to the formation of special three-dimensional net structure consisting of nanocrystalline (nc) TiN (TiAlN) encapsulated in an amorphous (a) Si3N4 matrix phase. Furthermore,the nc-TiAlN/a-Si3N4 coating shows the best machining performance.

Predictive plots for conical pick performance using mechanical and elastoplastic properties of rocks

Conical picks are by far the most widely used drag type cutting tools employed on partial face rock excavation machines.The cutting force and specific energy are two important design parameters for the conical pick performance,and the rock cutting testing is considered as the promising tool for determining these parameters.In the absence of an instrumented cutting rig,researchers generally rely on empirical predictive plots.For this,this paper suggests predictive plots for estimating the cutting force and specific energy,in consideration of the cutting depth to define the cuttability with conical picks.In this context,rock cutting tests were carried out on six volcanic rock samples with varying cutting depths using the unrelieved and relieved cutting modes.The cutting force and specific energy were correlated with the uniaxial compressive strength,Brazilian tensile strength,elasticity modulus,and plasticity index.Predictive plots were proposed for different cutting depths in the unrelieved and relieved cutting modes and exponential relationships were obtained among the cuttability parameters,and mechanical and elastoplastic properties of rocks.

Evaluation on cutting performance of novel PDC cutter for pipe jacking machine

It is inevitable to cut reinforced concrete(RC)appeared in cross passage of city metro by cutting tools when constructing in densely populated area.The previous cutters employed to cut RC are insufficient and easily damaged,so a new polycrystalline diamond compact(PDC)cutter is used to solve this question.Based on the theoretical analysis of cutting mechanism,both circular and tapered PDC cutters with cutting edge angle of 90and negative front rack angle of 10are used to cut RC.The peeling and breaking patterns of cutting concrete are proposed,the nodular and grainy chips are the preferred modes in cutting steel bars.The LS-DYNA is employed to investigate the cutting performance in advance.The simulation results show that the average and peak cutting forces increase with the growth of penetration depth,cutting speed,and roundness,and subsequently the recommended penetration depth less than 1.2 mm is obtained to cut RC due to the existence of steel bars.Moreover,the linear cutting platform is adopted to investigate the force ability and damage state of PDC cutters.It is concluded that the cutting force increases abruptly and fluctuates heavily when cutting the coarse aggregates.The patterns occurred in both numerical and experimental results are generally similar.Notably,the steel bar is pulled out and the PDC cutter is damaged at the penetration depth of 0.8 mm,while a good cut occurs at the penetration depth of 0.3 mm.The tapered PDC cutter with a relatively low cutting force is prone to be broken compared with circular PDC cutter.It is suggested that the circular PDC cutter at the penetration depth of 0.3 mm should be used to cut RC in practical engineering.

Ethernet Controller SoC Design and Its Low-Power DFT Considerations

In this paper, an Ethernet controller SoC solution and its low power design for testability （DFT） for information appliances are presented. On a single chip, an enhanced one-cycle 8-bit micro controller unit （MCU）, media access control （MAC） circuit and embedded memories such as static random access memory （SRAM）, read only memory （ROM） and flash are all integrated together. In order to achieve high fault coverage, at the same time with low test power, different DFT techniques are adopted for different circuits： the scan circuit that reduces switching activity is implemented for digital logic circuits; BIST-based method is employed for the on-chip SRAM and ROM. According to the fault-modeling of embedded flash, we resort to a March-like method for flash built in self test （BIST）. By all means above, the result shows that the fault coverage may reach 97%, and the SoC chip is implemented successfully by using 0.25 μm two-poly four-metal mixed signal complementary metal oxide semiconductor （CMOS） technology, the die area is 4.8×4.6 mm^2. Test results show that the maximum throughput of Ethemet packets may reach 7Mb·s^1.

Self-Cross-Linked Tannin-Aminated Tannin Surface Coatings for Particleboard

Aminated tannins were prepared by reacting mimosa condensed tannin extract with ammonia yielding the substitution of many,if not all of the tannin hydroxyl groups with–NH_(2)groups.A tannin-aminated tannin(ATT)particleboard coating was then prepared by reacting raw tannin extract with aminated tannin extract and thus cross-linking the two by substituting tannin’s hydroxyl groups with the–NH_(2)groups on the aminated tannin to form–NH-bridges between the two.The resulting particleboard coating gave encouraging results when pressed at 180℃for 3 min.Conversely,the system in which tannin was reacted/cross-liked with urea(ATU)by a similar amination reaction did not perform as well as the ATT system,and this even when a higher curing temperature and longer hot press time were used.In particular its water repellence was worse probably due to the presence of urea and such a system with lower reactivity.Nonetheless,substituting the tannin–OHs with the urea–NH_(2)groups appeared to also take place.ATT gave better results than ATU as regards water repellence and mechanical resistance as shown by the cross cut test.The ATT system was shown to be between 95%and 98%biosourced.The difference appeared to be due,by TMA analysis,to the much faster formation of the ATT hardened network leading to a better cross-linked polymer coating.The chemical species formed for both the ATT and ATU system were studied by MALDI ToF and CP MAS^(13)C NMR.